Integrating Your Persistence Framework into Your Application

Once you’ve generated your persistence framework with Service Builder, your next task is to bring all that functionality into your application. On the persistence side of things, Service Builder has generated all the basic functionality you’ll need for the Guestbook application. All you need to do is define the service layer, which is the buffer between your controller and your persistence layer. It is this layer that gives you the flexibility in your application to swap components in and out, should you decide that Service Builder is not for you.

First, you’ll implement a service layer for your Guestbook entity, and then you’ll implement one for your Entry entity.

Writing a Service API for Guestbooks

  1. Open the package. Service Builder has generated several stub classes for you here, two for each entity. The class is your implementation for local services, and the class is your implementation for remote services.

  2. Open the class. This is the core class you’ll customize in the service layer of your application. The controller (your portlet class) calls methods from here (not directly, but exposed via a -Util class), and the methods here call your service layer.

  3. It’s best to implement the simplest method first. What you’re doing here is exposing methods from the persistence layer in your service layer. Add the following two methods to your class:

    public List<Guestbook> getGuestbooks (long groupId) throws SystemException {
        return guestbookPersistence.findByGroupId(groupId);
    public List<Guestbook> getGuestbooks (long groupId, int start, int end)
       throws SystemException {
        return guestbookPersistence.findByGroupId(groupId, start, end);

    Notice that the work of actually going to the database and finding your Guestbook entities has already been done for you: all you’re doing is calling the generated methods. In a sense, you’re creating your own API for your application’s data. The first method gets all the entities that match a given groupId, and the second method does the same thing, but includes start and end markers to paginate the data.

Next, you’ll create a method to add a Guestbook entity. Remember in the last section how you created custom Exception classes for field validation? Now’s your chance to use them. Before you create a method for adding Guestbooks, you can create a method for validating them which you’ll use in the method that adds them:

protected void validate (String name) throws PortalException {
	if (Validator.isNull(name)) {
		throw new GuestbookNameException();

Use the IDE’s right click → SourceOrganize Imports facility to add Liferay’s com.liferay.portal.kernel.exception.PortalException, com.liferay.portal.kernel.util.Validator, and of course your to the class’s imports.

Now you’re ready to create a method that adds Guestbooks to the database.

  1. Add the following method signature:

    public Guestbook addGuestbook(long userId, String name, 
        ServiceContext serviceContext) throws SystemException, PortalException {

    Most of this makes sense at the moment: you know that you want the ID of the user who is adding the guestbook, along with its name. But what’s this ServiceContext thing? We’re glad you asked. Building on the Liferaypedia entry, ServiceContext is needed in order to pass information about the browsing session that triggered your method that adds a guestbook. Liferay uses the ServiceContext as a convenient container for relevant data like the current site, the current page, and more.

  2. Next, add the rest of the method:

     long groupId = serviceContext.getScopeGroupId();
     User user = userPersistence.findByPrimaryKey(userId);
     Date now = new Date();
     long guestbookId = counterLocalService.increment();
     Guestbook guestbook = guestbookPersistence.create(guestbookId);
     return guestbook;


    You can see how to get the groupId, which is the ID of the site the application is on, from the ServiceContext. You may want to use the code completion function of Liferay IDE/Developer Studio on the serviceContext variable to see what other information it carries.

    Next, you get the User object for the ID that was passed into the method, since you’ll need to populate its ID and full name attributes to your own Guestbook entity. After creating a Date with the current time in it, you call the validate(name) method you just created so that you can make sure the guestbook that somebody wants to create actually has a name. After this, you use Liferay’s database-agnostic primary key generator to create a new ID for your guestbook, and then you create the Guestbook entity that you’ll persist to the database once you populate it.

    All that’s left is to populate the entity’s fields, persist it, and return it to the caller.

Congratulations! You’ve successfully created a service API to retrieve and add Guestbooks. To enable it, you must run Service Builder again. When you do, it’ll generate the methods you just created in your service layer’s Interface classes. If you want, implement a similar method for updating a Guestbook. You already have the skills to do it.

Next, you’ll create similar methods for adding guestbook entries, and then you’ll move over the UI of your app and update it to take advantage of your new service and persistence layers.

Writing a Service API for Guestbook Entries

Now it’s time to do the same thing for the guestbook entries. You did the Guestbook entity first, because all Entry entities have a Guestbook as a foreign key, and also because quite frankly, it’s a simpler, smaller entity than Entry. Now that you have that experience under your belt, though, you’re ready to jump in and create a service API for guestbook entries.

  1. Open, which is in the same package as the class you’ve been working on,

  2. Create two methods for finding guestbook entries, like the methods you already created for Guestbook entities. Remember that the finder you created required two fields: a groupId and a guestbookId:

    public List<Entry> getEntries(long groupId, long guestbookId) throws SystemException {
        return entryPersistence.findByG_G(groupId, guestbookId);
    public List<Entry> getEntries(long groupId, long guestbookId, int start, int end)
         throws SystemException {
        return entryPersistence.findByG_G(groupId, guestbookId, start, end);
  3. Create a method for validating Entry objects. There are three required fields in an Entry object: name, email, and message. You can use Liferay’s included Validator to validate these fields:

    protected void validate (String name, String email, String entry) 
            throws PortalException {
        if (Validator.isNull(name)) {
            throw new EntryNameException();
        if (!Validator.isEmailAddress(email)) {
            throw new EntryEmailException();
        if (Validator.isNull(entry)) {
            throw new EntryMessageException();

    Notice that in addition to checking to make sure two String fields are not null, you’re also using the Validator to make sure a given String is an email address.

  4. Create a method for adding guestbook entries. This method is similar to the method you created earlier for adding guestbooks:

    public Entry addEntry(long userId, long guestbookId, String name,
            String email, String message, ServiceContext serviceContext)
             throws PortalException, SystemException {
        long groupId = serviceContext.getScopeGroupId();
        User user = userPersistence.findByPrimaryKey(userId);
        Date now = new Date();
        validate(name, email, message);
        long entryId = counterLocalService.increment();
        Entry entry = entryPersistence.create(entryId);
        return entry;

Excellent! You’ve now created a service API for both Guestbook and guestbook Entry entities. Now it’s time to modify your controller and view layers to make use of your new service API. You’ll do that in the next step.

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